Lodash常用用法总结

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玛尔斯通
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    Lodash是一个轻量级的JavaScript工具函数库，它方便了日常开发中对数据的操作，提高了开发效率。

    ​ 日常开发中，通常会对数据，特别是数组和对象进行各种读写等操作：比如去重，拷贝，合并，过滤，求交集，求和等等。根据平时开发中对数据的操作，我对Lodash常见的用法做了以下总结，方便今后的学习和整理。

    Array

    Create

    • 创建一个数组，元素为0, 1, 2, ... , 23

      _.range([start=0], end, [step=1])
      let arr = _.range(24)

console.log(arr) // [0, 1, 2, 3, ... , 23]

    • 创建一个数组，元素为100, 100, 100, 100, 100

      _.fill(array, value, [start=0], [end=array.length])
      let arr = _.fill(Array(5), 100)

console.log(arr) // [100, 100, 100, 100, 100]

    Read

    • 获取数组中最后一个元素

      _.last(array)
      let arr = [1, 2, 3, 4, 5]
let lastElement = _.last(arr) 

console.log(lastElement) // 5

    • 获取数组中倒数第二个元素

      _.nth(array, [n=0])
      let arr = [1, 2, 3, 4, 5]
let lastSecondElement = _.nth(-2) 

console.log(lastSecondElement) // 4

    • 获取对象数组中某一同名属性的属性值集合

      _.map(collection, [iteratee=_.identity])
      let users = [{
      id: 12,
      name: 'Adam',
      hobbies: [
        {name: 'running', index: 100},
        {name: 'cycling', index: 95}
      ]
   },{
      id: 14,
      name: 'Bob',
         hobbies: [
        {name: 'movie', index: 98},
        {name: 'music', index: 85}
      ]
   },{
      id: 16,
      name: 'Charlie',
      hobbies: [
       {name: 'travelling', index: 90},
       {name: 'fishing', index: 88}
      ]
   },{
      id: 18,
      name: 'David',
         hobbies: [
       {name: 'walking', index: 99},
       {name: 'football', index: 85}
     ]                 


   }
]
let userIds = _.map(users, 'id')
let mostFavouriteHobbies = _.map(users, 'hobbies[0].name')

console.log(userIds) // [12, 14, 16, 18]
console.log(mostFavouriteHobbies) // ["running", "movie", "travelling", "walking"]

    • 获取对象数组中某一属性值最大的对象

      _.maxBy(array, [iteratee=_.identity])
      let arr = [{a:1, b: 2, c: {d:4}}, {a:3, b: 4, c: {d:6}}]
let maxBObj = _.maxBy(arr, 'b')

console.log(maxBObj) // {a: 3, b: 4, c: {d: 6}}

    • 找出两个数组中元素值相同的元素

      _.intersection([arrays])
      let arr1 = [2, 1, {a: 1, b: 2}]
let arr2 = [2, 3, {a: 1, b: 2}]
let intersection = _.intersection(arr1, arr2) 

console.log(intersection) // [2]

    • 求数值数组中元素值的平均数

      _.mean(array)
      let numbers = [1, 2, 3, 4, 5]
let average = _.mean(numbers)

console.log(average) // 3

    • 求对象数组中某个属性值的平均数

      _.meanBy(array, [iteratee=_.identity])
      let objects = [{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }]
let average = _.meanBy(objects, 'n')

console.log(average) // 5

    • 获取数组中前n个元素，不改变原数组

      _.take(array, [n=1])
      let arr = [1, 2, 3, 4, 5]
let part1Arr = _.take(arr, 4)
let part2Arr = _.take(arr, 6)
let part3Arr = _.take([], 5)

console.log(part1Arr) // [1, 2, 3, 4]
console.log(part2Arr) // [1, 2, 3, 4, 5]
console.log(part3Arr) // []

    Delete

    • 删除数组中值为falsy的元素

      _.compact(array)
      let arr = [0, 1, false, 2, '', 3, null, undefined, NaN]
let truthyArr = _.compact(arr) 

console.log(truthyArr) // [1, 2, 3]

    Format

    • 去重。

      _.uniq(array)
      let arr = [2, 1, 2, '2', true]
let uniqArr = _.uniq(arr)

console.log(uniqArr) // [2, 1, '2', true]

    • 排序。对象数组，根据对象中的某个属性的值，升序或降序排序

      _.orderBy(collection, [iteratees=[_.identity]], [orders])
      let users = [
  {user: 'Tom', age: 25},
  {user: 'Amy', age: 23},
  {user: 'Perter', age: 22},
  {user: 'Ben', age: 29}
]
let sortedUsers = _.orderBy(users, 'age', 'desc')

console.log(sortedUsers)
// [{user: "Ben", age: 29}, {user: "Tom", age: 25}, {user: "Amy", age: 23}, {user: "Perter", age: 22}]

    • 分割数组[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]为 [1, 2, 3, 4, 5] 和 [6, 7, 8, 9, 10]

      _.chunk(array, [size=1])
      let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
let [left, right] = _.chunk(arr, 5)

console.log(left) // [1, 2, 3, 4, 5]
console.log(right) // [6, 7, 8, 9, 10]

    • 脱掉一层[]

      _.flatten(array)
      let address = {
  '江苏省': ['南京市', '苏州市'],
  '浙江省': ['杭州市', '绍兴市']
}
let cities = _.flatten(_.values(address))

console.log(cities) // ["南京市", "苏州市", "杭州市", "绍兴市"]

    • 将多维数组转为一维数组

      _.flattenDeep(array)
      let flattenedArr = _.flattenDeep([1, [2, [3, [4]], 5]]);

console.log(flattenedArr) // [1, 2, 3, 4, 5]

    Object

    Create

    • 通过数组["x", "y"] 和 数组[10, 10] 创建对象 {x: 10, y: 10}

      _.zipObject([props=[]], [values=[]])
      let keys = ["x", "y"]
let values = [10, 10]
let obj = _.zipObject(keys, values) 

console.log(obj) // {x: 10, y: 10}

    • 合并对象

      _.assign(object, [sources])
      let desObj = {name: '', gender: 'male', job: 'developer'}
let sourceObj = {name: 'Tom', job: ''}
let mergedObj = _.assign(desObj, sourceObj)

console.log(mergedObj) // {name: "Tom", gender: "male", job: ""}

    • 深拷贝对象

      _.cloneDeep(value)
      let sourceObj = {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14]}}
let desObj = _.cloneDeep(sourceObj)
desObj.permissions.store.push(15, 16)

console.log(desObj)
// {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14, 15, 16]}}
console.log(sourceObj)
// {department_id: 1, permissions: {management: [1, 2, 3, 4], store: [11, 12, 13, 14]}}

    • 合并多个对象中key值相同的键值对

      _.merge(object, [sources])
      let obj1 = {'9': {name: '乐购超市'}}
let obj2 = {'9': {storeToken: 'xxx'}}
let obj3 = {'9': {storePosition: 'Hangzhou'}}
let mergedObj = _.merge(obj1, obj2, obj3) 

console.log(mergedObj)
// 9: {name: "乐购超市", storeToken: "xxx", storePosition: "Hangzhou"}

    Read

    • 判断对象中是否有某个属性

      _.has(object, path)
      let obj = {a: [{b: {c: 3}}]}
let hasC = _.has(obj, 'a[0].b.c')

console.log(hasC) // true

    • 获取对象中的某个属性的值

      _.get(object, path, [defaultValue])
      let obj = {a: [{b: {c: 3}}]}
let c = _.get(obj, 'a[0].b.c')

console.log(c) // 3

    Update

    • 设置对象中的某个属性的值

      _.set(object, path, value)
      let obj = {a: [{b: {c: 3}}]}
let newObj = _.set(obj, 'a[0].b.c', 4);

console.log(obj.a[0].b.c); // 4

    • 对多个对象相同属性的属性值求和。

      let customers = {
  new_customer: {0: 33, 1: 5, ... , 23: 0},
  old_customer: {0: 22, 1: 7, ... , 24: 0}
}
let customer = {}
let keys = _.keys(customers.new_customer)
let values = _.values(customers)
_.map(keys, key => {
  customer[key] = _.sumBy(values, key)
})

customers.customer = customer

console.log(customers)
// console
{
    customer: {0: 55, 1: 12, ... , 23: 0}
  new_customer: {0: 33, 1: 5, ... , 23: 0}
  old_customer: {0: 22, 1: 7, ... , 23: 0}
}

    Number

    • 生成一个随机数，范围n~m

      _.random([lower=0], [upper=1], [floating])
      let random1 = _.random(2, 5)
let random2 = _.random(5)

console.log(random1) // 2, 3, 4, 5
console.log(random2) // 0, 1, 2, 3, 4, 5

    Data Type

    • 判断数据类型

      _.isNumber(value)

      _.isInteger(value)

      ...

      _.isPlainObject(value)

      let variable = 'hello';
// Number
console.log(_.isNumber(variable));
// Integer
console.log(_.isInteger(variable));
// Boolean
console.log(_.isBoolean(variable));
// String
console.log(_.isString(variable));
// Null
console.log(_.isNull(variable));
// Undefined
console.log(_.isUndefined(variable));
// Array
console.log(_.isArray(variable));
// Function
console.log(_.isFunction(variable));
// Object
console.log(_.isPlainObject(variable));
// Date
console.log(_.isDate(variable));

// DOM element
console.log(_.isElement(variable));

    • 数据类型转换

      • _.toArray

        _.toArray('abc') // ["a", "b", "c"]

      • _.toInteger

        _.toInteger(3.2); // 3
_.toInteger('3.2'); // 3

      • _.toNumber

        _.toNumber('3.2') // 3.2

      • _.toString

        _.toString(1); // "1"
_.toString([1, 2, 3]); // "1,2,3"

    Util

    • 重复多次某个元素

      _.times(n, [iteratee=_.identity])
      const dateParams = _.times(2, () => '2018-08-27');
console.log(dateParams) // ["2018-08-27", "2018-08-27"]
    lodashjavascript
    玛尔斯通
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    a cyclist, runner and coder.

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